Apparatus and method for processing groups of fields in a video data compression system

Abstract

A video compression system which is based on the image data compression system developed by the Motion Picture Experts Group (MPEG) uses various group-of-fields configurations to reduce the number of binary bits used to represent an image composed of odd and even fields of video information, where each pair of odd and even fields defines a frame. According to a first method, each field in the group of fields is predicted using the closest field which has previously been predicted as an anchor field. According to a second method, intra fields (I-fields) and predictive fields (P-fields) are distributed in the sequence so that no two I-fields and/or no two P-fields are at adjacent locations in the sequence. According to a third method, the number of I-fields and P-fields in the encoded sequence is reduced by encoding one field in a given frame as a P-field or a B-field where the other field is encoded as an I-field and encoding one field in a further frame as a B-field where the other field is encoded as a P-field.

The invention claimed is: 
     
       1. A method for automatically encoding a sequence of video image fields comprising the steps of: encoding each field in said sequence of video image fields in a predetermined order to produce a sequence of encoded fields wherein a plurality of the fields in the sequence of video image fields are bidirectionally predictively encoded;   decoding each field in the sequence of encoded fields to produce a sequence of decoded fields; and   storing each field in said sequence of decoded fields to produce a sequence of stored fields; wherein, each field in said sequence of video image fields which is bidirectionally predictively encoded is encoded using data from one of said stored fields which is closest in position in said sequence of video image fields to the field being bidirectionally predictively encoded.     
     
     
       2. The method of claim 1, wherein said sequence of video image fields are interleaved even and odd fields arranged so that each pair of even and odd fields forms a frame, and said method further includes the step of predictively encoding one of the odd and even fields of one frame as a P-field when the other one of the odd and even fields of the one frame has been encoded as an I-field, using only information in the one other field. 
     
     
       3. A method for automatically encoding sequential fields of video information comprising the steps of: encoding a first one of said sequential fields using only the video information in the first field to produce an I-field;   predictively encoding a second one of said sequential fields, separated from said first field by a plurality of field intervals, using the video information in the first and second fields to produce a P-field;   predictively encoding a third one of said sequential fields, occupying a position in the sequence between said first field and said second field, using the video information in the third field and in one of the first and second fields to produce a first B-field; and   predictively encoding a fourth one of said sequential fields, occupying a position in the sequence between said second field and said third field, using the video information in the fourth field and in one of the first, second and third fields to produce a second B-field.   
     
     
       4. A method according to claim 3, wherein said sequential fields of video information are interleaved even and odd fields arranged so that each pair of even and odd fields forms a frame, and said method further includes the step of encoding one of the odd and even fields of one frame as a B-field when the other one of the odd and even fields of the one frame has been encoded as a P-field. 
     
     
       5. A method according to claim 4, wheerin the encoded fields are arranged in the same sequence as said sequential fields and each P-field is separated from the next P-field by at least one B-field. 
     
     
       6. A method according to claim 4, wherein the encoded fields are arranged in the same sequence as said sequential fields and each I-field is separated from the next I-field by at least one B-field. 
     
     
       7. The method of claim 3, wherein said sequential fields of video information are interleaved even and odd fields arranged so that each pair of even and odd fields forms a frame, and said method further includes the step of encoding one of the odd and even fields of one frame as a B-field when the other one of the odd and even fields of the one frame has been encoded as an I-field. 
     
     
       8. A method for automatically encoding sequential interleaved even and odd fields of video information wherein each pair of even and odd fields forms a frame of video information, said method comprising the steps of: encoding one of the even fields of video information predictively using only information in the one even field and in a predecessor field occurring earlier in the sequence; and   encoding the odd field in the same frame as the one even field, bidirectionally predictively using information in the odd field, information in the one even field and information in a successor field occurring later in the sequence than the odd field.   
     
     
       9. The method of claim 8, further including the step of encoding an even field which immediately follows said one even field and said odd field in the sequence bidirectionally predictively using information in the odd field, information in the one even field and information in the successor field. 
     
     
       10. A video data compression system which encodes sequential fields of video information comprising: means for encoding a first one of said sequential fields using only the video information in the first field to produce an I-field.   means for predictively encoding a second one of said sequential fields, separated from said first field by a plurality of field intervals, using the video information in the first and second fields to produce a P-field;   means for predictively encoding a third one of said sequential fields, occupying a position in the sequence between said first field and said second field, using the video information in the third field and in one of the first and second fields to produce a first B-field; and   means for predictively encoding a forth one of said sequential fields, occupying a position in the sequence between said second field and said third field, using the video information in the fourth field and in one of the first, second and third fields to produce a second B-field.   
     
     
       11. A video data compression system which encodes sequential interleaved even and odd fields of video information wherein each pair of even and odd fields forms a frame of video information, said system comprising: means for encoding one of the even fields of video information predictively using only information in the one even field and in a predecessor field occurring earlier in the sequence; and   means for encoding the odd field in the same frame as the one even field, bidirectionally predictively using information in the odd field, information in the one even field and information in a successor field occurring later in the sequence than the odd field.   
     
     
       12. Apparatus for automatically encoding a sequence of video image fields comprising: means for encoding each field in said sequence of video image fields in a predetermined order to produce a sequence of encoded fields, wherein a plurality of the fields in the sequence are bidirectionally predictively encoded;   means for decoding each field in the sequence of encoded fields to produce a sequence of decoded fields; and   means for storing each field in said sequence of decoded fields to provide a sequence of stored fields; wherein, each field in said sequence of video image fields which is bidirectionally predictively encoded uses data from one of said stored fields which is closest in position in said sequence of video image fields to the field being bidirectionally predictively encoded.